Servais has been with Club Brugge since 2017. The 17-year-old left winger joined from the youth academy of Sporting Charleroi. In July 2020, Mathis signed a professional contract with Blauw-Zwart. In the same year, he made his debut for Club NXT U23 in the Challenger Pro League.
During the preparations for the 2022-2023 season, he gained playing time in friendly matches with the first team and even managed to score a beautiful freekick.